Selective catalytic reduction articles and systems

ABSTRACT

The present disclosure relates to copper-containing molecular sieve catalysts that are highly suitable for the treatment of exhaust containing NOx pollutants. The copper-containing molecular sieve catalysts contain ion-exchanged copper as Cu+2 and Cu(OH)+1, and DRIFT spectroscopy of the catalyst exhibits perturbed T-O-T vibrational peaks corresponding to the Cu+2 and Cu(OH)+1. In spectra taken of the catalytic materials, a ratio of the Cu+2 to the Cu(OH)+1 peak integration areas preferably can be ≥1. The copper-containing molecular sieve catalysts are aging stable such that the peak integration area percentage of the Cu+2 peak (area Cu+2/(area Cu+2+area Cu(OH)+1)) increases by ≤20% upon aging at 800° C. for 16 hours in the presence of 10% H2O/air, compared to the fresh state.

FIELD OF THE DISCLOSURE

The present disclosure relates to selective catalytic reduction (SCR)catalysts, catalytic articles, systems and methods suitable for treatingexhaust of an internal combustion engine.

BACKGROUND

Molecular sieves such as zeolites are employed in the catalysis ofcertain chemical reactions for example the selective catalytic reduction(SCR) of nitrogen oxides with a reductant such as ammonia, urea orhydrocarbons. Zeolites are crystalline materials having rather uniformpore sizes which range from about 3 to about 25 Angstroms in diameter,depending upon the type of zeolite.

Catalysts employed in the SCR process must be able to retain goodcatalytic activity over the wide range of temperatures found inpractical applications, including hydrothermal conditions withtemperatures ranging, for example, from about 150° C. to about 800° C.or higher. Hydrothermal conditions are encountered by SCR catalysts, aswater is a byproduct of fuel combustion. High temperature hydrothermalconditions occur in exhaust applications, for example, during theregeneration of a diesel particulate filter (DPF) or catalyzed sootfilter (CSF), a component of exhaust gas treatment systems used for theremoval of carbonaceous particles.

The SCR process converts nitrogen oxides (NOx) to nitrogen (N₂) andwater (H₂O). Nitrogen oxides (NOx) may include N₂O, NO, N₂O₃, NO₂, N₂O₄,N₂O₅ or HNO₃. It would be desirable to have improved articles, systemsand processes to convert NOx selectively within internal combustionengine exhaust streams to N₂. Improvements in high temperaturehydrothermal durability are required for short duration transients whereexhaust temperatures may reach 750° C., 800° C., 850° C. or even 900° C.Particularly important are improvements in low temperature NOxperformance, for example from about 150° C. to about 300° C., after hightemperature hydrothermal aging.

SUMMARY OF THE DISCLOSURE

The present disclosure provides, in some embodiments, acopper-containing molecular sieve catalyst, wherein the catalyst in afresh state contains ion-exchanged copper wherein 50 at % (atomicpercent) of the ion-exchanged copper is Cu⁺².

In further embodiments, the present disclosure can provide acopper-containing molecular sieve catalyst having a silica-to-aluminaratio (SAR) of about 5 to about 35 or about 14 to about 28 and a Cu/AIatomic ratio of about 0.20 to about 0.50.

In other embodiments, the present disclosure can provide acopper-containing molecular sieve catalyst, wherein the catalyst in afresh state contains ion-exchanged copper as Cu⁺² and Cu(OH)⁺¹ andwhere, in a DRIFT spectrum of the catalyst exhibiting a perturbed T-O-Tasymmetric stretching vibrational peak corresponding to Cu⁺² cations anda perturbed T-O-T asymmetric stretching vibrational peak correspondingto Cu(OH)⁺¹ cations, the ratio of the peak integration area for therespective Cu⁺² and Cu(OH)⁺¹ peaks is 1.

In yet other embodiments, the present disclosure can provide acopper-containing catalyst wherein the catalyst in a fresh statecontains ion-exchanged copper as Cu⁺² and Cu(OH)⁺¹ and where, in a DRIFTspectrum of the catalyst exhibiting a T-O-T asymmetric stretchingvibrational peak corresponding to Cu⁺² and a T-O-T asymmetric stretchingvibrational peak corresponding to Cu(OH)⁺¹, the percent of integratedpeak area of the T-O-T asymmetric stretching vibrational peakcorresponding to Cu⁺² relative to the total integrated areas of theT-O-T asymmetric stretching vibrational peaks corresponding to both Cu⁺²and Cu(OH)⁺¹ (i.e., area Cu⁺²/(area Cu⁺²+area Cu(OH)⁺¹)) increases by20%, 15%, 10%, or 5% upon aging at 800° C. for 16 hours in the presenceof 10% H₂O/air, compared to the fresh state.

The present disclosure also can provide a catalytic article comprising acatalytic coating disposed over a substrate, where the catalytic coatingcomprises one or more coating layers, wherein at least one coating layeris a catalytic coating layer comprising a copper-containing molecularsieve catalyst as described above.

The present disclosure further can provide an exhaust gas treatmentsystem comprising the catalytic article, as well as a method fortreating an exhaust stream containing NOx, the method comprising passingthe exhaust stream through the catalytic article or treatment system.

The present catalysts, catalytic articles, systems and methods areparticularly suitable for the treatment of exhaust gases generated fromdiesel or gasoline engines, especially those which operate under “lean”combustion conditions with air present in excess of that required forstoichiometric combustion.

The invention includes, without limitation, the following embodiments.

Embodiment 1

A selective catalytic reduction article comprising a substrate having acatalytic coating on at least a portion of a surface thereof, thecatalytic coating including a copper-containing molecular sievecontaining ion-exchanged copper as Cu⁺² cations and as Cu(OH)⁺¹ cations,wherein the copper-containing molecular sieve exhibits a perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationsand a perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu(OH)⁺¹ cations, and wherein an integrated peakarea of the perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu⁺² cations and an integrated peak area of theperturbed T-O-T asymmetric stretching vibrational peak corresponding tothe Cu(OH)⁺¹ cations have a ratio of as measured using DiffuseReflectance Infrared Fourier Transform (DRIFT) spectroscopy.

Embodiment 2

The selective catalytic reduction article of any preceding embodiment,wherein the copper-containing molecular sieve exhibits the perturbedT-O-T asymmetric stretching vibrational peaks corresponding to the Cu⁺²cations and the Cu(OH)⁺¹ cations at about 900 cm⁻¹ and about 950 cm⁻¹,respectively, in the infrared spectrum, or wherein the copper-containingmolecular sieve exhibits the perturbed T-O-T asymmetric stretchingvibrational peaks corresponding to the Cu⁺² cations and the Cu(OH)⁺¹cations at about 900 cm⁻¹ and about 970 cm⁻¹, respectively, in theinfrared spectrum.

Embodiment 3

The selective catalytic reduction article of any preceding embodiment,wherein a percentage of the total integrated peak area that isattributable to the perturbed T-O-T asymmetric stretching vibrationalpeak corresponding to the Cu⁺² cations is calculated by dividing theintegrated peak area for the perturbed T-O-T asymmetric stretchingvibrational peak corresponding to the Cu⁺² cations by the integratedpeak areas for the perturbed T-O-T asymmetric stretching vibrationalpeaks corresponding to the Cu⁺² cations and Cu(OH)⁺¹ cations combined,and wherein the percentage of the total integrated peak area that isattributable to the perturbed T-O-T asymmetric stretching vibrationalpeak for Cu⁺² cations is 50%.

Embodiment 4

The selective catalytic reduction article of any preceding embodiment,wherein the contribution by the perturbed T-O-T asymmetric stretchingvibrational peak corresponding to the Cu⁺² cations to the combinedintegrated peak areas for the perturbed T-O-T asymmetric stretchingvibrational peaks of the Cu⁺² cations and Cu(OH)⁺¹ cations for thecopper-containing molecular sieve in an aged state is increased by 20%relative to the contribution for the copper-containing molecular sievein the fresh state, wherein the aged state is defined by having aged theselective catalytic reduction article at a temperature of about 800° C.for a time of about 16 hours in the presence of air with an H₂O contentof about 10 mol. %.

Embodiment 5

The selective catalytic reduction article of any preceding embodiment,wherein the total amount of copper in the copper-containing molecularsieve, calculated as copper oxide, is about 1.0 wt. % to about 10 wt. %,based on the total weight of the copper-containing molecular sieve.

Embodiment 6

The selective catalytic reduction article of any preceding embodiment,wherein the copper-containing molecular sieve comprises crystals oragglomerates having a mean size 2.0 microns.

Embodiment 7

The selective catalytic reduction article of any preceding embodiment,wherein the copper-containing molecular sieve comprises a small poremolecular sieve selected from the group consisting of framework typesAEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV,LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC,UFI, mixtures thereof, and intergrowths thereof.

Embodiment 8

The selective catalytic reduction article of any preceding embodiment,wherein the molecular sieve comprises a medium pore molecular sieveselected from the group consisting of framework types AEL, AFO, AHT,BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR,JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MW, MWW, NAB, NAT, NES, OBW,PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR, SZR,TER, TON, TUN, UOS, VSV, WEI, WEN, mixtures thereof, and intergrowthsthereof.

Embodiment 9

The selective catalytic reduction article of any preceding embodiment,wherein the molecular sieve comprises a large pore molecular sieveselected from the group consisting of framework types AFI, AFR, AFS,AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT,EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF,LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF,SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY,USI, UWY, VET, mixtures thereof, and intergrowths thereof.

Embodiment 10

The selective catalytic reduction article of any preceding embodiment,wherein the molecular sieve is selected from the group consisting ofaluminosilicate zeolites, borosilicates, gallosilicates, SAPOs, AIPOs,MeAPSOs, MeAPOs, and combinations thereof.

Embodiment 11

The selective catalytic reduction article of any preceding claim,wherein the molecular sieve has CHA cages and double-six ring buildingunits and is selected from the group consisting of Cu-CHA, Cu-SAPO-34,AEI, Cu-SAPO-18, and combinations thereof.

Embodiment 12

The selective catalytic reduction article of any preceding embodiment,wherein the selective catalytic reduction article further comprises oneor more catalytically active metals selected from the group consistingof manganese, iron, cobalt, nickel, cerium, platinum, palladium andrhodium; or containing one or more base metals selected from the groupconsisting of sodium, potassium, magnesium, calcium, strontium, barium,and combinations thereof.

Embodiment 13

The selective catalytic reduction article of any preceding embodiment,wherein the catalytic coating comprises: a first catalytic coatingcomprising the copper-containing molecular sieve, and a second catalyticcoating that is different from the first catalytic coating.

Embodiment 14

The selective catalytic reduction article of any preceding embodiment,wherein the second catalytic coating comprises a copper-containingmolecular sieve that is different from the copper-containing molecularsieve in the first coating.

Embodiment 15

The selective catalytic reduction article of any preceding embodiment,wherein the second catalytic coating comprises a platinum group metal ona refractory metal oxide support.

Embodiment 16

The selective catalytic reduction article of any preceding embodiment,wherein the platinum group metal is present in an amount of about 0.5g/ft³ to about 30 g/ft³, based on the total volume of the substrate.

Embodiment 17

The selective catalytic reduction article of any preceding embodiment,wherein the catalytic coating including the copper-containing molecularsieve is present in an amount of about 0.1 g/in³ to about 4.5 g/in³,based on the total volume of the substrate.

Embodiment 18

The selective catalytic reduction article of any preceding embodiment,wherein the first catalytic coating and the second catalytic coating arein a layered configuration or zoned configuration.

Embodiment 19

The selective catalytic reduction article of any preceding embodiment,wherein the substrate is a porous wall-flow filter or a flow-throughmonolith.

Embodiment 20

An exhaust gas treatment system comprising: a selective catalyticreduction article according to any preceding embodiment; and a reductantinjector in fluid communication with and upstream of the selectivecatalytic reduction article.

Embodiment 21

The exhaust gas treatment system of any preceding embodiment, furthercomprising one or more of a diesel oxidation catalyst, a soot filter, alean NOx trap (LNT), and an ammonia oxidation catalyst.

Embodiment 22

A method for treating an exhaust stream containing NOx, comprisingpassing the exhaust stream through a selective catalytic reductionarticle or an exhaust gas treatment system of any preceding embodiment.

Embodiment 23

A method for identifying a catalytic material that is stable towardsaging, the method comprising: providing a plurality of samples that eachcomprise particles of a copper-containing molecular sieve containingion-exchanged copper as Cu⁺² cations and as Cu(OH)⁺¹ cations; subjectingthe particles of the copper-containing molecular sieve to DiffuseReflectance Infrared Fourier Transform (DRIFT) spectroscopy so as toevaluate perturbed T-O-T asymmetric stretching vibrational peakscorresponding to the Cu⁺² cations in the copper-containing molecularsieve and perturbed T-O-T asymmetric stretching vibrational peakscorresponding to the Cu(OH)⁺¹ cations in the copper-containing molecularsieve; and selecting one or more of the samples wherein thecopper-containing molecular sieve exhibits a ratio for an integratedpeak area of the perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu⁺² cations to an integrated peak area of theperturbed T-O-T asymmetric stretching vibrational peak corresponding tothe Cu(OH)⁺¹ cations that is ≥1.

Embodiment 24

The method of any preceding embodiment, wherein a percentage of thetotal integrated peak area that is attributable to the perturbed T-O-Tbond vibrational peak corresponding to the Cu⁺² cations is calculated bydividing the integrated peak area for the perturbed T-O-T bondvibrational peak corresponding to the Cu⁺² cations by the integratedpeak areas for the perturbed T-O-T bond vibrational peak correspondingto the Cu⁺² cations and the perturbed T-O-T bond vibrational peakcorresponding to the Cu(OH)⁺¹ cations combined, and wherein the methodcomprises selecting one or more samples wherein the percentage of thetotal integrated peak area that is attributable to the perturbed T-O-Tbond vibrational peak for Cu⁺² cations is ≥50%.

Embodiment 25

The method of any preceding embodiment, wherein the plurality ofcopper-containing molecular sieve samples is subjected to the DRIFTspectroscopy in a fresh state, and wherein the method further comprises:

aging the plurality of samples at a temperature of about 800° C. for atime of about 16 hours in the presence of air with an H₂O content ofabout 10 mol. % to form aged samples;

subjecting the aged samples to the DRIFT spectroscopy; and

selecting one or more of the samples wherein the contribution to thetotal integrated peak area by the perturbed T-O-T asymmetric stretchingvibrational peak corresponding to the Cu⁺² cations for the one or moresamples in an aged state is increased by 20% relative to thecontribution to the total integrated peak area by the perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationsfor the one or more samples in the fresh state.

Embodiment 26

A method of manufacturing a catalytic article, the method comprising:developing a process for preparing a first composition comprisingcopper-containing molecular sieves; analyzing at least a sample of thefirst composition using DRIFT spectroscopy to determine the relativeamount of Cu⁺² and Cu(OH)⁺¹ in the first composition based on acomparison of intensities of perturbed T-O-T asymmetric stretchingvibrational peaks corresponding to the Cu⁺² and Cu(OH)⁺¹; selecting theprocess for commercial manufacturing of the first composition if thecontribution by the perturbed T-O-T asymmetric stretching vibrationalpeak corresponding to Cu⁺² to the total integrated peak areas of theperturbed T-O-T asymmetric stretching vibrational peaks is ≥50%; andapplying the commercially manufactured first composition made by theprocess to a substrate to produce the catalytic article.

These and other features, aspects, and advantages of the disclosure willbe apparent from a reading of the following detailed descriptiontogether with the accompanying drawings, which are briefly describedbelow. The invention includes any combination of two, three, four, ormore of the above-noted embodiments as well as combinations of any two,three, four, or more features or elements set forth in this disclosure,regardless of whether such features or elements are expressly combinedin a specific embodiment description herein. This disclosure is intendedto be read holistically such that any separable features or elements ofthe disclosed invention, in any of its various aspects and embodiments,should be viewed as intended to be combinable unless the context clearlydictates otherwise. Other aspects and advantages of the presentinvention will become apparent from the following.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure described herein is illustrated by way of example and notby way of limitation in the accompanying figures. For simplicity andclarity of illustration, features illustrated in the figures are notnecessarily drawn to scale. For example, the dimensions of some featuresmay be exaggerated relative to other features for clarity. Further,where considered appropriate, reference labels have been repeated amongthe figures to indicate corresponding or analogous elements.

FIG. 1 is a perspective view of a honeycomb-type substrate carrier whichmay comprise a catalyst article in the form of a washcoat composition inaccordance with the present disclosure.

FIG. 2 is a partial cross-sectional view enlarged relative to FIG. 1 andtaken along a plane parallel to the end faces of the substrate carrierof FIG. 1, which shows an enlarged view of a plurality of the gas flowpassages shown in FIG. 1, in an embodiment wherein the substrate carrieris a monolithic flow-through substrate.

FIG. 3 is a cutaway view of a section enlarged relative to FIG. 1,wherein the honeycomb-type substrate carrier in FIG. 1 represents a wallflow filter substrate monolith.

FIG. 4a is a cross-section showing coating layers and/or coating zoneson one or more substrates according to exemplary embodiments of thepresent disclosure.

FIG. 4b is a cross-section showing coating layers and/or coating zoneson one or more substrates according to exemplary embodiments of thepresent disclosure

FIG. 5 is a graph showing NOx conversion of catalytic coating samples asdescribed in Example 1 and Example 2.

FIG. 6 is a graph showing NOx conversion of catalytic coating samples asdescribed in Example 1 and Example 3.

FIG. 7 illustrates the DRIFT spectra of catalytic coating samples asdescribed in Examples 1 through 3 in the fresh state.

FIG. 8 illustrates the DRIFT spectra of catalytic coating samples asdescribed in Example 1 in a fresh state and an aged state.

FIG. 9 illustrates the DRIFT spectra of catalytic coating samples asdescribed in Example 3 in a fresh state and an aged state.

FIG. 10 is a graph showing NOx conversion of catalytic coating samplesas described in Example 3 and Example 6.

FIG. 11 illustrates the DRIFT spectra of catalytic coating samples asdescribed in Example 6 in a fresh state and an aged state.

DETAILED DESCRIPTION

The present catalyst compositions are suitable for treatment of exhaustgas streams of internal combustion engines, for example gasoline,light-duty diesel and heavy duty diesel engines. The catalystcompositions are also suitable for treatment of emissions fromstationary industrial processes or for catalysis in chemical reactionprocesses.

High surface area refractory metal oxide supports are materials used ascatalyst supports that receive precious metals, stabilizers, promoters,binders and the like through association, dispersion, impregnation orother suitable methods. High surface area refractory metal oxidesupports can comprise an activated compound selected from the groupconsisting of alumina, zirconia, silica, titania, ceria, lanthana, bariaand combinations thereof.

Molecular Sieves

Molecular sieves refer to materials having an extensivethree-dimensional network of oxygen ions containing generallytetrahedral type sites and having a pore distribution of relativelyuniform pore size. A zeolite is a specific example of a molecular sieve,further including silicon and aluminum. Reference to a“non-zeolite-support” or “non-zeolitic support” in a catalyst layerrefers to a material that is not a zeolite. Examples of suchnon-zeolitic supports include, but are not limited to, high surface arearefractory metal oxides.

Molecular sieves comprise small pore, medium pore, and large poremolecular sieves or combinations thereof. A small pore molecular sievecontains channels defined by up to eight tetrahedral atoms. A mediumpore molecular sieve contains channels defined by ten-membered rings. Alarge pore molecular sieve contains channels defined by rings of atleast twelve tetrahedral atoms.

Small pore molecular sieves have an 8-ring opening and may have forinstance a double 6-ring (D6R) or 6-ring structural unit. The cagebuilding units include the CHA cage, various modifications of the CHAcage, LTA cage, GME cage and the like.

Small pore molecular sieves are selected from the group consisting ofaluminosilicate molecular sieves, metal-containing aluminosilicatemolecular sieves, aluminophosphate (ALPO) molecular sieves,metal-containing aluminophosphate (MeALPO) molecular sieves,silico-aluminophosphate (SAPO) molecular sieves, and metal-containingsilico-aluminophosphate (MeSAPO) molecular sieves and mixtures thereof.For example, small pore molecular sieves are selected from the groupconsisting of framework types AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB,EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE,RTH, SAS, SAT, SAV, SFW, TSC, UFI and mixtures or intergrowths thereof.For instance, the small pore molecular sieve is selected from the groupof framework types CHA, LEV, AEI, AFT, AFX, ERI, LTA, SFW, KFI and DDR.

Medium pore molecular sieves are selected from the group consisting offramework types AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER,HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT,MVY, MVWV, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG,STF, STI, STT, STW, SVR, SZR, TER, TON, TUN, UOS, VSV, WEI, WEN andmixtures or intergrowths thereof. For instance, the medium poremolecular sieves are selected from the group consisting of frameworktypes FER, MEL, MFI and STT.

Large pore molecular sieves are selected from the group consisting offramework types AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH,BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG,IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO,OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS,SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, VET and mixtures or intergrowthsthereof. For instance, the large pore molecular sieves are selected fromthe group consisting of framework types AFI, BEA, FAU, MAZ, MOR and OFF.

For example, molecular sieves comprise a framework type selected fromthe group consisting of AEI, BEA (beta zeolites), CHA (chabazite), FAU(zeolite Y), FER (ferrierite), MFI (ZSM-5) and MOR (mordenite).Non-limiting examples of zeolites having these structures includechabazite, faujasite, zeolite Y, ultrastable zeolite Y, beta zeolite,mordenite, silicalite, zeolite X and ZSM-5.

Useful molecular sieves have 8-ring pore openings and double-six ringsecondary building units, for example, those having structure types AEI,AFT, AFX, CHA, EAB, ERI, KFI, LEV, SAS, SAT or SAV. Included are any andall isotopic framework materials such as SAPO, ALPO and MeAPO materialshaving the same structure type.

Aluminosilicate zeolite structures do not include phosphorus or othermetals isomorphically substituted in the framework. That is,“aluminosilicate zeolite” excludes aluminophosphate materials such asSAPO, ALPO and MeAPO materials, while the broader term “zeolite”includes aluminosilicates and aluminophosphates.

In one or more embodiments, the 8-ring small pore molecular sieve hasthe CHA crystal structure. Copper-containing chabazite is abbreviated asCuCHA. In further embodiments, the molecular sieve can have the SAPOcrystal structure—i.e., CuSAPO.

A synthetic 8-ring small pore molecular sieve (for example having theCHA structure) may be prepared via mixing a source of silica, a sourceof alumina and a structure directing agent under alkaline aqueousconditions. Typical silica sources include various types of fumedsilica, precipitated silica and colloidal silica, as well as siliconalkoxides. Typical alumina sources include boehmites, pseudo-boehmites,aluminum hydroxides, aluminum salts such as aluminum sulfite or sodiumaluminate and aluminum alkoxides. Sodium hydroxide is typically added tothe reaction mixture. A typical structure directing agent for thissynthesis is adamantyltrimethyl ammonium hydroxide, although otheramines and/or quaternary ammonium salts may be substituted or added. Thereaction mixture is heated in a pressure vessel with stirring to yield acrystalline product. Typical reaction temperatures are in the range offrom about 100° C. to about 200° C., for instance from about 135° C. toabout 170° C. Typical reaction times are between 1 hr and 30 days and insome embodiments, from 10 hours to 3 days. At the conclusion of thereaction, the pH is optionally adjusted to between 6 and 10, for examplebetween 7 and 7.5 and the product is filtered and washed with water. Anyacid can be used for pH adjustment, for instance nitric acid.Optionally, the product may be centrifuged. Organic additives may beused to help with the handling and isolation of the solid product.Spray-drying is an optional step in the processing of the product. Thesolid product is thermally treated in air or nitrogen. Alternatively,each gas treatment can be applied in various sequences or mixtures ofgases can be applied. Typical calcination temperatures are in from about400° C. to about 850° C.

Molecular sieves having a CHA structure may be prepared for instanceaccording to methods disclosed in U.S. Pat. Nos. 4,544,538 and6,709,644, the disclosures of which are incorporated herein byreference.

The molecular sieves may have a silica-to-alumina ratio (SAR) of about 1to about 1000. In some embodiments, the molecular sieve may have an SARof about 2 to about 750, about 5 to about 250, or about 5 to about 50.

Advantageously, the molecular sieves of the present catalystcompositions are small pore, medium pore or large pore molecular sieves.

Catalytic Molecular Sieves

The catalyst for example contains ion-exchanged copper where the atomicpercentage (atomic % or at %) of ion-exchanged copper in a Cu⁺² state ina fresh sample compared to the atomic % of ion-exchanged copper in aCu⁺² state in the sample aged at 800° C. for 16 hours in the presence of10% H₂O/air remains stable. As further described herein, such stabilityhas been found to be highly desirable in identifying catalytic materialswith improved NOx conversion activity. Preferably, the atomicpercentages for a fresh sample versus an aged sample are within 20%,within 15%, within 10%, or within 5% of each other. The atomicpercentage of ion-exchanged copper in Cu⁺² state means relative to allion-exchanged copper.

In the present invention, the copper present in the ion-exchange sites(ion-exchanged copper) of the molecular sieves is 50 at % (atomicpercent) Cu⁺². Other ion-exchanged copper is in the form of, forexample, Cu(OH)⁺¹. This is after exposure to air and/or moisture andthus after oxidation. The Cu⁺² atomic percentage is determined basedupon analysis of infrared spectra of fresh and aged samples that allowfor identification of the relative copper species present in thecopper-exchanged catalytic material.

In some embodiments, the ion-exchanged copper may be identified forinstance via DRIFT spectroscopy (Diffuse Reflectance Infrared FourierTransform spectroscopy) carried out using known methods. Copper speciesmay be detected by monitoring perturbed T-O-T bond (Si—O—Al and Si—O—Si)vibrations of a molecular sieve. Structural vibrations of T-O-T bonds ofmolecular sieves exhibit absorption peaks from about 1350 cm⁻¹ to about920 cm⁻¹ and about 850 cm⁻¹ to about 620 cm⁻¹ for asymmetric andsymmetric vibration modes, respectively. Perturbed T-O-T bond vibrationsare observed when copper ions are exchanged into cationic positions of amolecular sieve, due to strong interactions between copper ions andframework oxygen. Peak positions depend on the nature of the copper ionsand the structure of the molecular sieve framework. Peak intensity andpeak integrated area can depend on the quantity of copper ions in theexchange sites. Accordingly, DRIFT spectroscopy is effective forqualitative analysis of the nature of the copper-exchanged molecularsieve catalytic material. In general, this invention contemplates usingfor characterization any vibrational modes that are perturbed (i.e.,shifted) due to the presence of different species of metallic ionsinteracting with the T-O-T framework of the molecular sieves. Forexample, as disclosed herein, copper species may be detected bymonitoring perturbed T-O-T asymmetric stretching vibrational modes byusing DRIFT spectroscopy.

DRIFT spectroscopy may be performed as in the present Examples. See,also, Luo et al., “Identification of two types of Cu sites in Cu/SSZ-13and their unique responses to hydrothermal aging and sulfur poisoning,”Catalysis Today, 267 (2016), 3-9; and Kwak et al., “two differentcationic positions in Cu-SSZ-13?,” Chem. Commun., 2012, 48, 4758-4760.

In DRIFT spectra of aluminosilicate chabazite CuCHA, in addition to theasymmetric and symmetric vibrations of unperturbed T-O-T (Si—O—Al) bondsat ca. 1040 and ca. 810 cm⁻¹, two absorptions are observed at ca. 900cm⁻¹ and ca. 950 cm⁻¹, attributed to a perturbed T-O-T asymmetricstretching vibration with Cu⁺² associated with an Al pair and aperturbed T-O-T asymmetric stretching vibration with Cu(OH)⁺¹ associatedwith a single Al, respectively. In the present disclosure, the term“exhibiting a Cu⁺² peak and a Cu(OH)⁺¹ peak” refers to the perturbedabsorptions that are identified in the DRIFT spectra. For example, inthe case of a copper chabazite catalytic material, infrared absorptionsat ca. 900 cm⁻¹ and ca. 950 cm⁻¹ corresponding to perturbed T-O-Tasymmetric stretching vibrations can be correlated to the presence ofCu⁺² and Cu(OH)⁺¹, respectively. Similarly, in the case of a copper SAPOcatalytic material, infrared absorptions at ca. 900 cm⁻¹ and ca. 970cm⁻¹ corresponding to perturbed asymmetric stretching vibrations can becorrelated to the presence of Cu⁺² and Cu(OH)⁺¹, respectively.

Without being bound by theory, it is believed that Cu⁺² balancing thecharge of an Al pair is more hydrothermally stable than Cu(OH)⁺¹associated with a single Al, thus providing catalysts capable of highNOx reduction activity and high hydrothermal stability. Also withoutbeing bound by theory, it is believed that Cu cations balance the chargecreated by Si substituting for P in a SAPO molecular sieve. Theperturbed T-O-T bond vibrations for SAPO are related to the structuralvibrations due to the Si, Al and P in the tetrahedral “T” sites. Assuch, catalysts with a higher relative percentage of Cu⁺² in themolecular sieve framework (as determined via DRIFT analysis as discussedabove through identification of perturbed T-O-T bonds, such as thosecorresponding to perturbed T-O-T asymmetric stretching vibrations) canbe identified and can provide improved catalytic performance and agingstability.

In some embodiments, preferred stability can be associated with adefined ratio between the integrated peak area of the perturbed T-O-Tasymmetric stretching peak corresponding to the Cu⁺² cations (e.g., thepeak for perturbed T-O-T bonds at about 900 cm⁻¹ in a DRIFT spectrum)and the integrated peak area of the perturbed T-O-T asymmetricstretching peak corresponding to the Cu(OH)⁺¹ cations (e.g., the peakfor perturbed T-O-T bonds at about 950 cm⁻¹ in a DRIFT spectrum forCuCHA or at about 970 cm⁻¹ in a DRIFT spectrum for CuSAPO). For example,the ratio of the integrated peak area for perturbed T-O-T asymmetricstretching peaks corresponding to Cu⁺² relative to peaks correspondingto Cu(OH)⁻¹ can be or For example, the ratio of the integrated peakareas can be about 1 to about 5 about 1.2 to about 4, or about 1.5 toabout 3.

In further embodiments, suitable copper-exchanged molecular sieves canbe identified in relation to the contribution to the total peak area ofthe perturbed T-O-T asymmetric stretching vibrational peaks by theperturbed T-O-T asymmetric stretching vibrational peak for Cu⁺². Thiscan be calculated using the formula provided below, wherein “area Cu⁺²”is the integrated peak area perturbed T-O-T asymmetric stretchingvibrational peaks corresponding to Cu⁺² (i.e., the peak at about 900cm⁻¹ in the DRIFT spectrum), and “area Cu(OH)⁺¹” is the integrated peakarea for perturbed T-O-T asymmetric stretching vibrational peakscorresponding to Cu(OH)⁺¹ (i.e., the peak at about 950 cm⁻¹ in the DRIFTspectrum for CuCHA and at about 970 cm⁻¹ in the DRIFT spectrum forCuSAPO).

$\frac{( {{area}\mspace{14mu} {Cu}^{+ 2}} )}{( {{{area}\mspace{14mu} {Cu}^{+ 2}} + {{area}\mspace{14mu} {{Cu}({OH})}^{+ 1}}} )}$

Preferably, the percentage of the total peak area that is attributableto the perturbed T-O-T asymmetric stretching vibrational peak for Cu⁺²is at least 50%, at least 55%, or at least 60%, such as about 55% toabout 95%, about 60% to about 90%, or about 65% to about 85%.

While the integrated area under the respective curves for the perturbedabsorptions presently has not been correlated to an amount of therelative atomic % of the individual copper species present, maintenanceof the ratio with aging is clearly indicative of a stable structure andhas been correlated to a material with stable catalytic activity.

In some embodiments, the foregoing ratio and percentage may besubstantially unchanged between the fresh state and the aged state forthe copper-exchanged molecular sieve. For example, after thecopper-exchanged molecular sieve has been aged at a temperature of about800° C. for a time of about 16 hours in the presence of air with an H₂Ocontent of about 10 mol %, the percentage of the total peak areacorresponding to perturbed T-O-T asymmetric stretching vibrations thatis attributable to the perturbed T-O-T asymmetric stretching vibrationalpeak for Cu⁺² can be increased by ≤30%, ≤20%, or ≤10%.

Without being bound by theory, it is believed that all molecular sievesconstructed from CHA and double-six rings will exhibit similarvibrational modes, and that Cu cations will perturb the vibrationalspectra in a similar manner. Such molecular sieves are CHA, SAPO-34, AEIand SAPO-18. Other small, medium and large molecular sieves will exhibittheir own unique vibrational spectra, and Cu cations will perturb thevibrational modes in a similar manner.

The copper-containing molecular sieves are prepared for example viaion-exchange from for example a Na⁺ containing molecular sieve (Na⁺form). The Na⁺ form generally refers to the calcined form without anyion exchange. In this form, the molecular sieve generally contains amixture of Na⁺ and H⁺ cations in the exchange sites. The fraction ofsites occupied by Na⁺ cations varies depending on the specific zeolitebatch and recipe. Optionally, the alkali metal molecular sieves are NH₄⁺-exchanged and the NH₄ ⁺ form is employed for ion-exchange with copper.Optionally, the NH₄ ⁺-exchanged molecular sieve is calcined to theH⁺-form which may also be employed for ion-exchange with copper.

Copper is ion-exchanged into molecular sieves with alkali metal, NH₄ ⁺or H⁺ forms with copper salts such as copper acetate, copper sulfate andthe like, for example as disclosed in U.S. Pat. No. 9,242,238, thedisclosure of which is incorporated herein by reference. For instance aNa⁺, NH₄ ⁺ or H⁺ form of a molecular sieve is mixed with an aqueous saltsolution and agitated at an elevated temperature for a suitable time.The slurry is filtered and the filter cake is washed and dried.

Further, at least a portion of a catalytically active metal may beincluded during a molecular sieve synthetic process such that a tailoredcolloid contains a structure directing agent, a silica source, analumina source and a metal ion (e.g. copper) source, as disclosed inU.S. Pat. No. 9,272,272, the disclosure of which is incorporated hereinby reference.

The total amount of copper in the molecular sieve is for example about1.0 wt. % to about 10 wt. %, based on the total weight of thecopper-containing molecular sieve. In some embodiments, the total amountof copper in the molecular sieve can be about 1.5 wt. % to about 9 wt.%, about 2.0 wt. % to about 8 wt. %, or about 3.0 wt. % to about 7 wt.%, based on the total weight of the copper-containing molecular sieve.

The total amount of copper includes ion-exchanged copper and copperassociated with the molecular sieve but not ion-exchanged.

Amounts of copper in a molecular sieve are reported as the oxide, CuO.The total dry weight of the molecular sieve includes the anyadded/exchanged metals like copper.

The total amount of copper in a molecular sieve, for example analuminosilicate zeolite, may also be defined by the copper-to-aluminumatomic ratio. For example, the Cu/AI atomic ratio may be about 0.20 toabout 0.50. In some embodiments, the Cu/AI atomic ratio can be about0.25 to about 0.50, about 0.3 to about 0.50, or about 0.35 to about0.50.

The molecular sieves containing copper may each have a sodium content(reported as Na₂O on a volatile free basis) of below 2 wt. %, based onthe total weight of the catalyst composition. In more specificembodiments, sodium content is below 2500 ppm. The molecular sieves mayeach have an atomic sodium-to-aluminum ratio of less than about 0.7, forexample about 0.02 to about 0.7. The molecular sieves may each have anatomic copper to sodium ratio of greater than about 0.5, for exampleabout 0.5 to about 50.

The present copper-containing molecular sieves may exhibit a BET surfacearea, determined according to DIN 66131, of at least about 400 m²/g, atleast about 550 m²/g, or at least about 650 m²/g, for example, about 400to about 750 m²/g or, about 500 to about 750 m²/g. The present molecularsieves may have a mean crystal size of about 10 nanometers to about 20microns, preferably about 0.1 microns to about 2.0 microns as determinedvia Scanning Electron Microscopy (SEM). Advantageously, the mean crystalsize is 0.5 microns or 2.0 microns.

Catalytic Coating/Substrate

The molecular sieves may be provided in the form of a powder or aspray-dried material which is admixed with or coated with suitablemodifiers. Modifiers include silica, alumina, titania, zirconia andrefractory metal oxide binders (for example a zirconium precursor). Thepowder or the sprayed material, optionally after admixing or coating bysuitable modifiers, may be formed into a slurry, for example with water,which is deposited upon a suitable substrate as part of a catalyticcoating, disclosed for example in U.S. Pat. No. 8,404,203, thedisclosure of which is incorporated herein by reference.

A catalytic coating contains one or more carriers containing activecatalytic species. A catalytic coating may typically be applied in theform of a washcoat containing carriers having catalytically activespecies thereon. A washcoat is formed by preparing a slurry containing aspecified solids content (e.g., 10-60% by weight) of carriers in aliquid vehicle, which is then coated onto a substrate and dried andcalcined to provide a coating layer. When multiple coating layers areapplied, the substrate is dried and/or calcined after each layer isapplied. A final calcination step is performed after the number ofdesired multiple layers are applied.

Coating layers of molecular sieves may be prepared using a binder, forexample, a ZrO₂ binder derived from a suitable precursor such aszirconyl acetate or any other suitable zirconium precursor such aszirconyl nitrate. Zirconyl acetate binder provides a catalytic coatingthat remains homogeneous and intact after thermal aging, for example,when the catalyst is exposed to high temperatures of at least about 600°C., for example, about 800° C. and higher, and high water vaporenvironments of about 5% or 10% or more. Other potentially suitablebinders include, but are not limited to, alumina and silica. Aluminabinders include aluminum oxides, aluminum hydroxides, and aluminumoxyhydroxides. Aluminum salts and colloidal forms of alumina many alsobe used. Silica binders include various forms of SiO₂, includingcolloidal silica. Binder compositions may include any combination ofzirconia, alumina, and silica.

Any of present coating layers may contain ZrO₂ and/or Al₂O₃ binders.

The term “catalyst” or “catalyst composition” refers to a material thatpromotes a chemical reaction. The catalyst includes the “catalyticallyactive species” and the “carrier” that carries or supports the activespecies. For example, molecular sieves including zeolites arecarriers/supports for present copper active catalytic species. Likewise,refractory metal oxide particles may be a carrier for platinum groupmetal catalytic species.

Present copper-containing catalysts are highly effective as selectivecatalytic reduction (SCR) catalysts of nitrogen oxides (NOx) to N₂.Typically, a reductant such as ammonia is employed. Urea may be employedas an ammonia precursor.

The catalytically active species are also termed “promoters” as theypromote chemical reactions. For instance, the present copper-containingmolecular sieves may be termed copper-promoted molecular sieves. A“promoted molecular sieve” refers to a molecular sieve to whichcatalytically active species are intentionally added.

The term “substrate” refers in general to a monolithic material ontowhich a catalytic coating is disposed, for example a flow-throughmonolith or monolithic wall-flow filter. In one or more embodiments, thesubstrate is a ceramic or metal having a honeycomb structure. Anysuitable substrate may be employed, such as a monolithic substrate ofthe type having fine, parallel gas flow passages extending from an inletend to an outlet end of the substrate such that passages are open tofluid flow. The passages, which are essentially straight paths fromtheir fluid inlet to their fluid outlet, are defined by walls on which acatalytic coating is disposed so that gases flowing through the passagescontact the catalytic material. The flow passages of the monolithicsubstrate are thin-walled channels, which can be of any suitablecross-sectional shape and size such as trapezoidal, rectangular, square,sinusoidal, hexagonal, oval, circular, etc. Such structures may containfrom about 60 to about 900 or more gas inlet openings (i.e. cells) persquare inch of cross-section.

Present substrates are 3-dimensional having a length and a diameter anda volume, similar to a cylinder. The shape does not necessarily have toconform to a cylinder. The length is an axial length defined by an inletend and an outlet end.

Flow-through monolith substrates for example have a volume of about 50in³ to about 1200 in³, a cell density of about 60 cells per square inch(cpsi) to about 500 cpsi or up to about 900 cpsi, for example about 200to about 400 cpsi and a wall thickness of about 50 to about 150 micronsor about 200 microns.

The substrate may be a “flow-through” monolith as described above.Alternatively, a catalytic coating may be disposed on a wall-flow dieselparticulate filter (DPF), thus producing a catalyzed soot filter (CSF)or Catalyzed DPF (CDPF). If a wall-flow substrate is utilized, theresulting system will be able to remove particulate matter along withgaseous pollutants. The wall-flow filter substrate can be made frommaterials commonly known in the art, such as cordierite, aluminumtitanate or silicon carbide. Loading of the catalytic coating on awall-flow substrate will depend on substrate properties such as porosityand wall thickness and typically will be lower than the catalyst loadingon a flow-through substrate.

Wall-flow filter substrates useful for supporting the SCR catalyticcoatings have a plurality of fine, substantially parallel gas flowpassages extending along the longitudinal axis of the substrate.Typically, each passage is blocked at one end of the substrate body,with alternate passages blocked at opposite end-faces. Such monolithiccarriers may contain up to about 700 or more flow passages (or “cells”)per square inch of cross-section, although far fewer may be used. Forexample, the typical carrier usually has from about 100 to about 300,cells per square inch (“cpsi”). The cells can have cross-sections thatare rectangular, square, circular, oval, triangular, hexagonal, or areof other polygonal shapes. Wall-flow substrates typically have a wallthickness from about 150 microns to about 500 microns, for example fromabout 200 microns to about 350 microns. Wall-flow filters will generallyhave a wall porosity of at least 40% with an average pore size of atleast 10 microns prior to disposition of the catalytic coating. Forinstance, wall-flow filters will have a wall porosity of from about 50to about 75% and an average pore size of from about 10 to about 30microns prior to disposition of a catalytic coating.

FIGS. 1 and 2 illustrate an exemplary substrate 2 in the form of aflow-through substrate coated with a washcoat composition as describedherein. Referring to FIG. 1, the exemplary substrate 2 has a cylindricalshape and a cylindrical outer surface 4, an upstream end face 6 and acorresponding downstream end face 8, which is identical to end face 6.Substrate 2 has a plurality of fine, parallel gas flow passages 10formed therein. As seen in FIG. 2, flow passages 10 are formed by walls12 and extend through carrier 2 from upstream end face 6 to downstreamend face 8, the passages 10 being unobstructed so as to permit the flowof a fluid, e.g., a gas stream, longitudinally through carrier 2 via gasflow passages 10 thereof. As more easily seen in FIG. 2, walls 12 are sodimensioned and configured that gas flow passages 10 have asubstantially regular polygonal shape. As shown, the washcoatcomposition can be applied in multiple, distinct layers if desired. Inthe illustrated embodiment, the washcoat consists of both a discretebottom washcoat layer 14 adhered to the walls 12 of the carrier memberand a second discrete top washcoat layer 16 coated over the bottomwashcoat layer 14. The present invention can be practiced with one ormore (e.g., 2, 3, or 4) washcoat layers and is not limited to theillustrated two-layer embodiment.

Alternatively, FIGS. 1 and 3 can illustrate an exemplary substrate 2 inthe form a wall flow filter substrate coated with a washcoat compositionas described herein. As seen in FIG. 3, the exemplary substrate 2 has aplurality of passages 52. The passages are tubularly enclosed by theinternal walls 53 of the filter substrate. The substrate has an inletend 54 and an outlet end 56. Alternate passages are plugged at the inletend with inlet plugs 58, and at the outlet end with outlet plugs 60 toform opposing checkerboard patterns at the inlet 54 and outlet 56. A gasstream 62 enters through the unplugged channel inlet 64, is stopped byoutlet plug 60 and diffuses through channel walls 53 (which are porous)to the outlet side 66. The gas cannot pass back to the inlet side ofwalls because of inlet plugs 58. The porous wall flow filter used inthis invention is catalyzed in that the wall of said element has thereonor contained therein one or more catalytic materials. Catalyticmaterials may be present on the inlet side of the element wall alone,the outlet side alone, both the inlet and outlet sides, or the wallitself may consist all, or in part, of the catalytic material. Thisinvention includes the use of one or more layers of catalytic materialon the inlet and/or outlet walls of the element.

Catalyzed wall-flow filters are disclosed for instance in U.S. Pat. No.7,229,597, the disclosure of which is incorporated here by reference.This reference teaches a method of applying a catalytic coating suchthat the coating permeates the porous walls, that is, is dispersedthroughout the walls. Flow-through and wall-flow substrates are alsotaught for example in U.S. Pat. app. No. 62/072,687, published asWO2016/070090.

The present catalytic coating may be on the wall surface and/or in thepores of the walls, that is “in” and/or “on” the filter walls. Thus, thephrase “having a catalytic coating thereon” means on any surface, forexample on a wall surface and/or on a pore surface.

The inlet end of a substrate is synonymous with the “upstream” end or“front” end. The outlet end is synonymous with the “downstream” end or“rear” end. A substrate will have a length and a width.

The ceramic substrate may be made of any suitable refractory material,e.g. cordierite, cordierite-α-alumina, aluminum titanate, siliconcarbide, silicon nitride, zircon mullite, spodumene,alumina-silica-magnesia, zircon silicate, sillimanite, a magnesiumsilicate, zircon, petalite, α-alumina, an aluminosilicate and the like.

Substrates useful in the present invention may also be metallic,comprising one or more metals or metal alloys. The metallic substratesmay be employed in various shapes such as pellets, corrugated sheet ormonolithic foam. Specific examples of metallic substrates includeheat-resistant, base-metal alloys, especially those in which iron is asubstantial or major component. Such alloys may contain one or more ofnickel, chromium, and aluminum, and the total of these metals mayadvantageously comprise at least about 15 wt. % (weight percent) of thealloy, for instance, about 10 to about 25 wt. % chromium, about 1 toabout 8 wt. % of aluminum, and from 0 to about 20 wt. % of nickel.

The catalytic coating comprises one or more thin adherent coatinglayers, where at least one coating layer comprises the copper-containingcatalyst. The coating is disposed on and in adherence to the substrate.The entire coating comprises the individual “coating layers”. Thecatalytic coating may be “zoned”, comprising zoned catalyst layers. Thismay also be described as “laterally zoned”. For example, a first layermay extend from the inlet end towards the outlet end extending fromabout 10 to about 90%, about 10% to about 50%, or about 10% to about 25%of the substrate length. A second layer may extend from the outlet endtowards the inlet end extending from about 10% to about 90%, about 10%to about 50%, or about 10% to about 25% of the substrate length. Thefirst and second layers may be adjacent to each other and not overlayeach other. Alternatively, the first and second layers may overlay aportion of each other, providing a third “middle” zone. The middle zonemay for example extend from about 5% to about 80% of the substratelength. Alternatively, the first layer may extend from the outlet endand the second layer may extend from the inlet end.

An upstream zone is upstream of a downstream zone. A zone of a catalyzedsubstrate is defined as a cross-section having a certain coatingstructure thereon.

First and second layers may each extend the entire length of thesubstrate or may each extend a portion of the length of the substrateand may overlay or underlay each other, either partially or entirely.Each of the first and second layers may extend from either the inlet oroutlet end. Coating layers that overlay or underlay each other,partially or entirely, may be termed “top” and “bottom” coating layers,where the top layer is “over” the bottom layer. The top layer over thebottom layer means they may be in direct contact or may have aninterlayer in-between.

First and/or second coating layers may be in direct contact with thesubstrate. Alternatively, one or more “undercoats” may be present, sothat at least a portion of the first and/or the second coating layersare not in direct contact with the substrate (but rather with theundercoat). One or more “overcoats” may also be present, so that atleast a portion of the first and/or second coating layers are notdirectly exposed to a gaseous stream or atmosphere (but rather are incontact with the overcoat).

First and second coating layers may be in direct contact with each otherwithout a “middle” overlapping zone. Alternatively, the first and secondcoating layers may not be in direct contact, with a “gap” between thetwo zones. In the case of an “undercoat” or “overcoat” the gap betweenthe first and second SCR layer is termed an “interlayer.”

An undercoat is a layer “under” a further coating layer, an overcoat isa layer “over” a further coating layer and an interlayer is a layer“between” two further coating layers.

The interlayer(s), undercoat(s) and overcoat(s) may contain one or morecatalysts or may be free of catalysts.

The present catalytic coatings may comprise more than one identicallayer, for instance more than one identical layer comprising the presentcopper-containing catalyst.

FIGS. 4a and 4b show some possible coating layer configurations with twocoating layers. Shown are substrate walls 200 onto which coating layers201 (top coat) and 202 (bottom coat) are disposed. This is a simplifiedillustration, and in the case of a porous wall-flow substrate, not shownare pores and coatings in adherence to pore walls and not shown areplugged ends. In FIG. 4a , bottom coating layer 202 extends from theoutlet about 50% of the substrate length and top coating layer 201extends from the inlet greater than 50% of the length and overlays aportion of layer 202, providing an upstream zone 203, a middle zone 205and a downstream zone 204. In FIG. 4b , coating layers 201 and 202 eachextend the entire length of the substrate with top layer 201 overlayingbottom layer 202. The substrate of FIG. 4b does not contain a zonedcoating configuration. In FIGS. 4a and 4b , either layer 201, 202 orboth may contain a present copper-containing molecular sieve. FIGS. 4aand 4b may be useful to illustrate coating compositions on thewall-through substrate or the flow-through substrate.

The present catalytic coating, as well as each zone of a catalyticcoating or any section of a coating, is present on the substrate at aloading (concentration) of for instance about 0.3 g/in³ to about 4.5g/in³ based on the substrate. This refers to dry solids weight pervolume of substrate, for example per volume of a honeycomb monolith. Theamount of base metal, i.e. copper, is only a portion of the catalyticcoating, which also includes the molecular sieve. An amount of copperper volume would for instance be about 0.2% to about 10% of the abovevalues. An amount of copper per volume is the copper concentration. Anamount of a copper-containing molecular sieve per volume is themolecular sieve concentration. Concentration is based on a cross-sectionof a substrate or on an entire substrate.

Catalytic Articles and Systems

The term “catalytic article” refers to an element that is used topromote a desired reaction. The present catalytic articles comprise asubstrate having a catalytic coating disposed thereon.

A system contains more than one article, for instance, a first SCRarticle and a second SCR article. A system may also comprise one or morearticles containing a reductant injector, a diesel oxidation catalyst(DOC), a soot filter, an ammonia oxidation catalyst (AMOx) or a lean NOxtrap (LNT).

An article containing a reductant injector is a reduction article. Areduction system includes a reductant injector and/or a pump and/or areservoir, etc.

The present treatment system may further comprise a diesel oxidationcatalyst and/or a soot filter and/or an ammonia oxidation catalyst. Adiesel particulate filter (DPF) may be uncatalyzed or may be catalyzed,thus creating a catalyzed soot filter (CSF). For instance, the presenttreatment system may comprise, from upstream to downstream—an articlecontaining a DOC, a CSF, an urea injector, the present zoned SCR articleor a first SCR article and a second SCR article and an articlecontaining an AMOx.

An alternate system may contain a lean NOx trap (LNT) followed by a SCRcatalyst coated on a particulate filter (SCRoF) and optionally a zonedSCR article containing an AMOx catalyst. In this system both the SCRoFand SCR articles may contain the present catalysts.

An undercoat layer comprising an AMOx catalyst may be present in adownstream zone of a substrate. For instance an AMOx undercoat layer mayextend from the outlet end towards the inlet end about 10% to about 80%of the substrate length of a present article.

An AMOx layer may also be present on a second substrate of a seconddownstream article to provide a downstream AMOx article.

AMOx catalysts are taught for instance in U.S. Pub. No. 2011/0271664,the disclosure of which is incorporated herein by reference. An ammoniaoxidation (AMOx) catalyst may be a supported precious metal componentwhich is effective to remove ammonia from an exhaust gas stream. Theprecious metal may include ruthenium, rhodium, iridium, palladium,platinum, silver or gold. For example, the precious metal componentincludes physical mixtures or chemical or atomically-doped combinationsof precious metals. The precious metal component for instance includesplatinum. Platinum may be present in an amount of about 0.008% to about2 wt. % based on the AMOx catalyst.

The precious metal component is typically deposited on a high surfacearea refractory metal oxide support. Examples of suitable high surfacearea refractory metal oxides include alumina, silica, titania, ceria,and zirconia, as well as physical mixtures, chemical combinations and/oratomically-doped combinations thereof. In specific embodiments, therefractory metal oxide may contain a mixed oxide such as silica-alumina,amorphous or crystalline aluminosilicates, alumina-zirconia,alumina-lanthana, alumina-manganesia, alumina-baria, alumina-ceria andthe like. An exemplary refractory metal oxide comprises high surfacearea γ-alumina having a specific surface area of about 50 to about 300m²/g.

The AMOx catalyst may include a zeolitic or non-zeolitic molecular sievefor example selected from those of the AEI, CHA, FAU, BEA, MFI and MORtypes. A molecular sieve may be physically mixed with an oxide-supportedplatinum component. In an alternative embodiment, platinum may bedistributed on the external surface or in the channels, cavities orcages of the molecular sieve.

Present embodiments that include a first catalytic article and a secondcatalytic article may be referred to as a “multi-component” or“multi-brick” system. A “brick” may refer to a single article such as amonolith or filter.

Advantageously, articles of a multi-component system may each containsubstrates containing zoned or layered coatings as disclosed herein.

The catalytic articles are effective to catalyze the reduction ofnitrogen oxides (NOx) in the presence of a reductant, for exampleammonia or urea. In operation, the reductant is periodically meteredinto the exhaust stream from a position upstream of the SCR article. Theinjector is in fluid communication with and upstream of the SCR article.The injector may also be associated with a reductant reservoir and apump.

Present articles, systems and methods are suitable for treatment ofexhaust gas streams from mobile emissions sources such as trucks andautomobiles. Articles, systems and methods are also suitable fortreatment of exhaust streams from stationary sources such as powerplants.

Ammonia is a typical reductant for SCR reactions for treating exhaust ofstationary power plants while urea is the typical SCR reducing agentused for treatment of exhaust of mobile emissions sources. Ureadecomposes to ammonia and carbon dioxide prior to contact with or on theSCR catalyst, where ammonia serves as the reducing agent for NOx.

The articles, systems and methods described herein can provide highNO_(x) conversion. The term “fresh” defines the state of the catalystarticle immediately following preparation and the term “fresh catalystactivity” defines the catalyst performance in the “fresh” condition. Theterm “aged” defines the state of the catalyst article followinghydrothermal aging for a defined period of time, and the term “agedcatalyst activity” defines the catalyst performance in the “aged”condition. Catalyst performance can be defined in relation to a specifictest temperature. For example, a present catalytic article may exhibitan aged NO_(x) conversion at 200° C. of at least 50% and preferably atleast 75% (e.g., about 50% to about 99%) measured at a gas hourly spacevelocity of 80000 h⁻¹. A present catalytic article may exhibit an agedNO_(x) conversion at 450° C. of at least 70% and preferably at least 85%(e.g., about 70% to about 99% measured at a gas hourly volume-basedspace velocity of 80000 h⁻¹ under laboratory reactor steady stateconditions in a gas mixture of 500 ppm NO, 500 ppm NH₃, 10% O₂, 5% H₂O,balance N₂. An aged catalyst meeting the above requirements may besubject to aging conditions such that, prior to evaluation, thecatalysts are hydrothermally aged in a tube furnace in a gas flowcontaining 10% H₂O, 10% O₂, balance N₂ for 50 hours at 650° C., for 5hours at 750° C. or for 16 h at 800° C. Such SCR activity measurementsare demonstrated in U.S. Pat. No. 8,404,203.

SCR performances such as NO_(x) conversion are for example measured at agas hourly volume-based space velocity of 80000 h⁻¹ under pseudo-steadystate conditions in a gas mixture of 500 ppm NO_(x) (fast SCR condition:NO₂/NOx=0.5 or standard SCR conditions: NO₂/NOx=0), 500 ppm NH₃, 10% O₂,5% H₂O, balance N₂ in a temperature ramp of 0.5° C./min from 200° C. to600° C.

NOx conversion is defined as mol % conversion of NO and NO₂ combined. Ahigh value is desired.

The term “exhaust stream” or “exhaust gas stream” refers to anycombination of flowing gas that may contain solid or liquid particulatematter. The stream comprises gaseous components and is for exampleexhaust of a lean burn engine, which may contain certain non-gaseouscomponents such as liquid droplets, solid particulates and the like. Anexhaust stream of a lean burn engine typically further comprisescombustion products, products of incomplete combustion, oxides ofnitrogen, combustible and/or carbonaceous particulate matter (soot) andun-reacted oxygen and/or nitrogen.

In the present exhaust gas treatment methods, the exhaust gas stream ispassed through the SCR article, SCR system or exhaust gas treatmentsystem by entering the upstream end and exiting the downstream end.

Certain embodiments pertain to the use of articles, systems and methodsfor removing NOx from exhaust gases of internal combustion engines, inparticular diesel engines, which operate at combustion conditions withair in excess of that required for stoichiometric combustion, i.e. leanconditions.

The term “vehicle” means for instance any vehicle having an internalcombustion engine and includes for instance passenger automobiles, sportutility vehicles, minivans, vans, trucks, buses, refuse vehicles,freight trucks, construction vehicles, heavy equipment, militaryvehicles, farm vehicles and the like.

“Platinum group metal components” refer to platinum group metals or oneof their oxides. “Rare earth metal components” refer to one or moreoxides of the lanthanum series defined in the Periodic Table ofElements, including lanthanum, cerium, praseodymium and neodymium.

D90 particle size distribution indicates that 90% of the particles (bynumber) have a Feret diameter below a certain size as measured byScanning Electron Microscopy (SEM) or Transmission Electron Microscopy(TEM) for submicron size particles; and a particle size analyzer forsupport-containing particles (micron size). Average (mean) particle sizeis synonymous with D50, meaning half of the population resides abovethis point, and half below. Particle size may be measured by laser lightscattering techniques, with dispersions or dry powders, for exampleaccording to ASTM method D4464. A particle size analyzer measures thenumber distribution of individual particles as a function of size.Individual particles may be single crystallites or an agglomerate ofsmaller crystallites.

Identification of Aging Stable Catalytic Materials

As evident from the foregoing and from the appended Examples, thepresent disclosure can particularly relate to methods for identifyinguseful catalytic materials. The use of DRIFT spectroscopy in particularmakes it possible to evaluate a plurality of samples ofcopper-containing molecular sieves and identify materials that would beexpected to be useful as a catalytic material, and more particularly toidentify materials that can exhibit aging stability.

A method for identification of catalytic materials can comprise firstproviding a plurality of samples that each comprise particles of acopper-containing molecular sieve containing ion-exchanged copper asCu⁺² cations and as Cu(OH)⁺¹ cations. The copper-containing molecularsieve materials may have any configuration as otherwise describedherein.

The various samples can be in particulate form or may be milled asnecessary to provide the necessary form for subjecting the particles ofthe copper-containing molecular sieve to Diffuse Reflectance InfraredFourier Transform (DRIFT) spectroscopy. DRIFT spectroscopy can becarried out so as to evaluate perturbed T-O-T vibrational peakscorresponding to the Cu⁺² cations in the copper-containing molecularsieve and perturbed T-O-T vibrational peaks corresponding to theCu(OH)⁺¹ cations in the copper-containing molecular sieve. As otherwisedescribed herein, such information can be used to identify the nature ofthe copper cations in the copper-containing molecular sieve. Moreover,such information can be directly related to the NOx conversion activityand the aging stability that would be expected in the copper-containingmolecular sieve.

The present methods thus further can include selecting one or more ofthe samples whereby the DRIFT data indicates usefulness as otherwisediscussed herein. For example, a useful sample can be identified whereinthe copper-containing molecular sieve exhibits a ratio for an integratedpeak area of the perturbed T-O-T vibrational peak corresponding to theCu⁺² cations to a peak integration area of the perturbed T-O-Tvibrational peak corresponding to the Cu(OH)⁺¹ cations that is ≥1.

The further characteristics that are also described herein as indicatingusefulness may also be applied in the alternative or in any combinationfor identifying suitable samples for use in manufacturing catalyticcompositions or catalytic articles. For example, as already describedabove, a percentage of the total integrated peak area that isattributable to the integrated peak area for the perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationscan be calculated by dividing the integrated peak area for the perturbedT-O-T asymmetric stretching vibrational peak corresponding to the Cu⁺²cations by a total peak integration area for the perturbed T-O-T bondvibrational peak corresponding to the Cu⁺² cations and the perturbedT-O-T asymmetric stretching vibrational peak corresponding to theCu(OH)⁺¹ cations combined. With such knowledge, the present methods thuscan include selecting one or more samples wherein the percentage of thetotal integrated peak area that is attributable to the perturbed T-O-Tbond vibrational peak for Cu⁺² cations is 50%.

As desired, additional processing steps can be carried out to confirmaging stability of the useful samples. For example, the plurality ofsamples subjected to the DRIFT spectroscopy as discussed above canspecifically be in a fresh state. As such, the method further cancomprise aging the plurality of samples (e.g., at a temperature of about800° C. for a time of about 16 hours in the presence of air with an H₂Ocontent of about 10 mol %) to form aged samples. Thereafter, the methodscan comprise subjecting the aged samples to the DRIFT spectroscopy andselecting one or more of the samples, wherein the percentage of thetotal integrated peak area that is attributable to the perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationsfor the copper-containing molecular sieve in an aged state is increasedby 20% relative to the percentage of the total integrated peak area thatis attributable to the perturbed T-O-T asymmetric stretching vibrationalpeak corresponding to the Cu⁺² cations for the copper-containingmolecular sieve in the fresh state.

The foregoing methods thus make it possible to identify useful catalyticmaterials that can be expected to exhibit good NOx conversion activitiesand also be aging stable. As such, new catalytic materials can beidentified more easily based upon spectroscopic analysis without theneed for other detailed testing techniques.

The articles “a” and “an” herein refer to one or to more than one (e.g.at least one) of the grammatical object. Any ranges cited herein areinclusive. The term “about” used throughout is used to describe andaccount for small fluctuations. For instance, “about” may mean thenumeric value may be modified by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%,±0.3%, ±0.2%, ±0.1% or ±0.05%. All numeric values are modified by theterm “about” whether or not explicitly indicated. Numeric valuesmodified by the term “about” include the specific identified value. Forexample “about 5.0” includes 5.0.

Unless otherwise indicated, all parts and percentages are by weight.Weight percent (wt. %), if not otherwise indicated, is based on anentire composition free of any volatiles, that is, based on dry solidscontent.

All U.S. patent applications, published patent applications, and patentsreferred to herein are hereby incorporated by reference.

Example 1 SCR Catalyst

Catalytic coatings containing CuCHA zeolite having a SAR of 17, 4.0 wt.% CuO and a Cu/AI ratio of 0.295 and zirconium oxide binder weredisposed via a washcoat process on cellular ceramic monoliths having acell density of 400 cpsi and a wall thickness of 6 mil. The coatedmonoliths were dried at 110° C. and calcined at about 550° C. for 1hour. The coating process provided a catalyst loading of 2.1 g/in³ ofwhich 5% is zirconium oxide binder.

Example 2 SCR Catalyst

Catalytic coatings containing CuCHA zeolite having a SAR of 20, 3.8 wt.% CuO and a Cu/AI ratio of 0.325 and zirconium oxide binder weredisposed via a washcoat process on cellular ceramic monoliths having acell density of 400 cpsi and a wall thickness of 6 mil. The coatedmonoliths were dried at 110° C. and calcined at about 550° C. for 1hour. The coating process provided a catalyst loading of 2.1 g/in³ ofwhich 5% is zirconium oxide binder.

Example 3 SCR Catalyst

Catalytic coatings containing CuCHA zeolite having a SAR of 25, 3.5 wt.% CuO and a Cu/AI ratio of 0.365 and zirconium oxide binder weredisposed via a washcoat process on cellular ceramic monoliths having acell density of 400 cpsi and a wall thickness of 6 mil. The coatedmonoliths were dried at 110° C. and calcined at about 550° C. for 1hour. The coating process provided a catalyst loading of 2.1 g/in³ ofwhich 5% is zirconium oxide binder.

Example 4 NOx Conversion Testing for Catalytic Coatings from Examples1-3

NO_(x) conversions were measured in a laboratory reactor at a gas hourlyvolume-based space velocity of 80000 h⁻¹ under pseudo-steady stateconditions in a gas mixture of 500 ppm NO, 500 ppm NH₃, 10% O₂, 5% H₂O,balance N₂ in a temperature ramp of 0.5° C./min from 200° C. to 600° C.NOx conversion is reported as mol % and measured as NO and NO₂.

The coated monoliths of Examples 1-3 were hydrothermally aged in thepresence of 10% H₂O/air at 800° C. for 16 hours. FIG. 5 shows NOxconversion of Example 1 relative to Example 2. FIG. 6 shows NOxconversion of Example 1 relative to Example 3. Example 1 was superiorregarding NOx conversion under both aging conditions.

Example 5 DRIFT Spectroscopy for Catalytic Coatings from Examples 1-3

DRIFT measurements were performed on a THERMO NICOLET FT-IR instrumentwith a MCT (HgCdTe) detector and a Harrick environmental chamber withZnSe windows. Samples were ground to a fine powder with mortar andpestle and placed into the sample cup. The powder was dehydrated at 400°C. for 1 hour in flowing Ar at 40 mL/min and cooled to 30° C. and thespectra was recorded using KBr as a reference. Copper species in zeolitewere identified by monitoring the perturbed T-O-T bond (Si—O—Al andSi—O—Si) vibrations by infrared spectroscopy. The structural vibrationsof T-O-T bonds in zeolite have absorption peaks at 1350-920 cm⁻¹ and850-620 cm⁻¹ for asymmetric and symmetric vibration modes, respectively.The perturbed T-O-T bond vibrations are observed when copper ions areexchanged into cationic position of zeolite structures, due to stronginteraction between copper ions and neighbouring oxygen atoms in theframework. The peak position depends on the status of charge compensatedcations and the structure of the zeolite framework. The peak intensitydepends on the quantity of charge compensated cations in the exchangedsites.

DRIFT spectra of the CuCHA samples of Examples 1, 2 and 3 in the freshstate are shown in FIG. 7. In addition to the asymmetric and symmetricvibrations of unperturbed T-O-T (Si—O—Al) bonds at ca. 1040 and 810cm⁻¹, two new perturbed absorptions appeared at 900 and 950 cm⁻¹. Thepeak at 900 cm⁻¹ was attributed to perturbed T-O-T asymmetric stretchingvibrations with Cu²⁺ associated with an Al pair, and the peak at 950cm⁻¹ was attributed to perturbed T-O-T asymmetric stretching vibrationswith Cu(OH)⁺ associated with a single Al. Peak fitting was carried outin Origin 9.1 software. The peaks were modeled as Gaussian peaks andpeak fitting was performed until a chi-squared tolerance value of 1E-6was reached. The peak areas associated with the 900 and 950 cm⁻¹perturbed vibrational modes of the fresh samples are listed in Table 1.The perturbed T-O-T peak at 900 cm⁻¹ evidencing Cu²⁺ ion associated withan Al pair has the greatest area, implying that Cu⁺² is the dominantcopper species in Example 1, and the 900 cm⁻¹ peak area is 71% of thetotal peak areas including the sum of peak areas at 900 and 950 cm⁻¹.Examples 2 and 3 comprise a large quantity of Cu(OH)⁺¹ in addition toCu²⁺ (as evidenced by increased areas under the T-O-T peaks at 950 cm⁻¹)and the percentage of 900 cm⁻¹ peak area relative to the sum total ofthe peak areas including 900 and 950 cm⁻¹) was only 47% and 43%,respectively. Example 1 shows high NO, reduction activity and highhydrothermal stability; without being bound by theory, it is believedCu²⁺ ion balancing the charge of an Al pair is more stable than Cu(OH)⁺¹balancing the charge of a single Al.

Hydrothermal aging at 800° C. did not alter the relative T-O-T peakareas at 900 and 950 cm⁻¹ for the copper-exchanged molecular sieve inExample 1 as shown in FIG. 8 and Table 2. This is evidence that therelative atomic percentages of Cu⁺² and Cu(OH)⁺¹ in the copper-exchangedmolecular sieve in Example 1 likewise were unchanged by the aging, thusdemonstrating the high hydrothermal stability of Example 1. In the caseof Example 3, after 800° C. aging, the signal for the perturbed T-O-Tpeak evidencing the Cu(OH)⁺¹ (at 950 cm⁻¹) largely decreased and thesignal for the perturbed T-O-T peak evidencing the Cu²⁺ (at 900 cm⁻¹)increased (FIG. 9), resulting in the percentage of the 900 cm⁻¹ peakincreasing from 43% to 76% (Table 3). The total peak area decreased from382 to 320.

Without being bound by theory, it is important to note that it is notimplied that the Cu(OH)⁺¹ species is transformed to Cu⁺², but only thatthe relative ratio of Cu⁺² to the sum total of Cu cation species,[Cu⁺²+Cu(OH)⁺¹], is changing.

TABLE 1 IR peak fitting results of fresh samples Peak area Example ~950cm⁻¹ ~900 cm⁻¹ Total peak area % of A_(900 cm−1) Example 1 103 255 35871 Example 2 222 194 416 47 Example 3 216 166 382 43

TABLE 2 IR peak fitting results of Example 1 fresh and aged samples Peakarea Total Example 1 ~950 cm⁻¹ ~900 cm⁻¹ peak area % of A_(900 cm−1)Fresh 103 255 358 71 Aged at 800° C. 93 270 363 74

TABLE 3 IR peak fitting results of Example 3 fresh and aged samples Peakarea Total Example 3 ~950 cm⁻¹ ~900 cm⁻¹ peak area % of A_(900 cm−1)Fresh 216 166 382 43 Aged at 800° C. 78 242 320 76

It is seen that the % peak area of the 900 cm⁻¹ peak for thecopper-exchanged molecular sieve in Example 1 (% of A900_(cm-1))increases by only about 4% upon aging (3/71). The % peak area of the 900cm⁻¹ peak for the copper-exchanged molecular sieve in Example 3increased about 77% (33/43). Thus, the copper-exchanged molecular sieveof Example 1 showed the desired aging stability as well as the increasedNOx conversion performance as discussed in Example 4.

Example 6 SCR Catalyst

Catalytic materials containing CuSAPO were prepared. Specifically, Cuexchange using 0.2 M copper acetate was carried on NH₄-SAPO-34 at 80° C.for 2 hours. The sample was filtered, washed with DI water and dried at90° C. then calcined at 450° C. for 2 hours. The obtained CuSAPO-34 hada copper content of 3.3 wt. %, expressed as CuO. The CuSAPO material wasevaluated to confirm that the stability may be achieved for varioustypes of molecular sieves.

Example 7 NOx Conversion Testing

NOx conversions were measured in a laboratory reactor at a gas hourlyvolume-based space velocity of 80000 h⁻¹ under steady state conditionsin a gas mixture of 500 ppm NO, 500 ppm NH₃, 10% O₂, 5% H₂O, balance N₂in temperatures of 175, 200, 225, 250, 400, 550 and 575° C. NOxconversion was reported as mol % and measured as NO and NO₂. The CuSAPOfrom Example 6 and the CuCHA from Example 3 were hydrothermally aged inthe presence of 10% H₂O/air at 800° C. for 16 hours. FIG. 10 shows NOxconversion of Example 6 relative to Example 3. Example 6 shows high NOxconversion in the fresh state and after aging.

Example 8 DRIFT Spectroscopy for Example 6

DRIFT measurements were performed as described in Example 5. The DRIFTspectrum of the sample from Example 6 is shown in FIG. 11. PerturbedT-O-T bonds at ca. 900 and 970 cm⁻¹ are attributed to the asymmetricstretching vibration of the T-O-T bond with Cu²⁺ associated with a Sipair and the asymmetric stretching vibration of the T-O-T bond withCu(OH)⁺ associated with a single Si, respectively. Peak fitting wasagain carried out in Origin 9.1 software. In the peak fitting, the peakswere modeled as Gaussian peaks and peak fitting was performed until achi-squared tolerance value of 1E-6 was reached. As can be seen in FIG.11, the perturbed T-O-T peak at 900 cm⁻¹ evidencing Cu²⁺ ion associatedwith a Si pair has the greatest area implying that Cu⁺² was the dominantcopper species in Example 6.

Hydrothermal aging at 800° C. did not alter the relative T-O-T peakareas at 900 and 970 cm⁻¹ for the copper-exchanged SAPO-34 molecularsieve in Example 6. This is evidence that the relative atomicpercentages of Cu⁺² and Cu(OH)⁺¹ in the copper-exchanged SAPO-34molecular sieve in Example 6 likewise are unchanged by the aging, thusdemonstrating the high hydrothermal stability of Example 6.

Hydrothermal aging at 800° C. does not alter the quantity of Cu²⁺ andCu(OH)⁺ in Example 6 as shown in FIG. 11 and Table 4, demonstrating thehigh hydrothermal stability of Example 6. It is seen that the % peakarea of the 900 cm⁻¹ peak for inventive Example 1 and Example 6 (% ofA900_(cm-1)) increases by only about 4% upon aging (3/71 for Example 1and 3/73 for Example 6). The % peak area of the 900 cm⁻¹ peak forcomparative Example 3 increases about 77% (33/43).

TABLE 4 IR peak fitting results of Example 6 fresh and aged samples Peakarea Total Example 6 ~970 cm⁻¹ ~900 cm⁻¹ peak area % of A_(900 cm−1)Fresh 62 164 226 73 Aged at 800° C. 59 192 251 76

1. A selective catalytic reduction article comprising a substrate havinga catalytic coating on at least a portion of a surface thereof, thecatalytic coating including a copper-containing molecular sievecontaining ion-exchanged copper as Cu⁺² cations and as Cu(OH)⁺¹ cations,wherein the copper-containing molecular sieve exhibits a perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationsand a perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu(OH)⁺¹ cations, and wherein the integrated peakareas of the perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu⁺² cations and a perturbed T-O-T asymmetricstretching vibrational peak corresponding to the Cu(OH)⁺¹ cations have aratio of ≥1 as measured using Diffuse Reflectance Infrared FourierTransform (DRIFT) spectroscopy.
 2. The selective catalytic reductionarticle of claim 1, wherein the copper-containing molecular sieveexhibits the perturbed T-O-T asymmetric stretching vibrational peakscorresponding to the Cu⁺² cations and the Cu(OH)⁺¹ cations at about 900cm⁻¹ and about 950 cm⁻¹, respectively, in the infrared spectrum, orwherein the copper-containing molecular sieve exhibits perturbed T-O-Tasymmetric stretching vibrational peaks corresponding to the Cu⁺²cations and the Cu(OH)⁺¹ cations at about 900 cm⁻¹ and about 970 cm⁻¹,respectively, in the infrared spectrum.
 3. The selective catalyticreduction article of claim 1, wherein a percentage of the totalintegrated peak area that is attributable to the perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationsis calculated by dividing the integrated peak area for the perturbedT-O-T asymmetric stretching vibrational peak corresponding to the Cu⁺²cations by the integrated peak areas for the perturbed T-O-T asymmetricstretching vibrational peaks corresponding to the Cu⁺² cations andCu(OH)⁺¹ cations combined, and wherein the percentage of the totalintegrated peak area that is attributable to the perturbed T-O-Tasymmetric stretching vibrational peak for Cu⁺² cations is ≥50%.
 4. Theselective catalytic reduction article of claim 3, wherein thecontribution by the perturbed T-O-T asymmetric stretching vibrationalpeak corresponding to the Cu⁺² cations to the combined integrated peakareas for the perturbed T-O-T asymmetric stretching vibrational peaks ofthe Cu⁺² cations and Cu(OH)⁺¹ cations for the copper-containingmolecular sieve in an aged state is increased by ≤20% relative to thecontribution for the copper-containing molecular sieve in the freshstate, wherein the aged state is defined by having aged the selectivecatalytic reduction article at a temperature of about 800° C. for a timeof about 16 hours in the presence of air with an H₂O content of about 10mol. %.
 5. The selective catalytic reduction article of claim 1, whereinthe total amount of copper in the copper-containing molecular sieve,calculated as copper oxide, is about 1.0 wt. % to about 10 wt. %, basedon the total weight of the copper-containing molecular sieve.
 6. Theselective catalytic reduction article of claim 1, wherein thecopper-containing molecular sieve comprises crystals or agglomerateshaving a mean size ≤2.0 microns.
 7. The selective catalytic reductionarticle of claim 1, wherein the copper-containing molecular sievecomprises a small pore molecular sieve selected from the groupconsisting of framework types AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB,EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE,RTH, SAS, SAT, SAV, SFW, TSC, UFI, mixtures thereof, and intergrowthsthereof.
 8. The selective catalytic reduction article of claim 1,wherein the molecular sieve comprises a medium pore molecular sieveselected from the group consisting of framework types AEL, AFO, AHT,BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR,JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW,PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR, SZR,TER, TON, TUN, UOS, VSV, WEI, WEN, mixtures thereof, and intergrowthsthereof.
 9. The selective catalytic reduction article of claim 1,wherein the molecular sieve comprises a large pore molecular sieveselected from the group consisting of framework types AFI, AFR, AFS,AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT,EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF,LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF,SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY,USI, UWY, VET, mixtures thereof, and intergrowths thereof.
 10. Theselective catalytic reduction article of claim 1, wherein the molecularsieve is selected from the group consisting of aluminosilicate zeolites,borosilicates, gallosilicates, SAPOs, AlPOs, MeAPSOs, MeAPOs, andcombinations thereof.
 11. The selective catalytic reduction article ofclaim 1, wherein the molecular sieve has CHA cages and double-six ringbuilding units and is selected from the group consisting of Cu-CHA,Cu-SAPO-34, AEI, Cu-SAPO-18, and combinations thereof.
 12. The selectivecatalytic reduction article of claim 1, wherein the selective catalyticreduction article further comprises one or more catalytically activemetals selected from the group consisting of manganese, iron, cobalt,nickel, cerium, platinum, palladium and rhodium; or containing one ormore base metals selected from the group consisting of sodium,potassium, magnesium, calcium, strontium, barium, and combinationsthereof.
 13. The selective catalytic reduction article of claim 1,wherein the catalytic coating comprises: a first catalytic coatingcomprising the copper-containing molecular sieve; and a second catalyticcoating that is different from the first catalytic coating.
 14. Theselective catalytic reduction article of claim 13, wherein the secondcatalytic coating comprises a copper-containing molecular sieve that isdifferent from the copper-containing molecular sieve in the firstcoating.
 15. The selective catalytic reduction article of claim 13,wherein the second catalytic coating comprises a platinum group metal ona refractory metal oxide support.
 16. The selective catalytic reductionarticle of claim 15, wherein the platinum group metal is present in anamount of about 0.5 g/ft³ to about 30 g/ft³, based on the total volumeof the substrate.
 17. The selective catalytic reduction article of claim13, wherein the catalytic coating including the copper-containingmolecular sieve is present in an amount of about 0.1 g/in³ to about 4.5g/in³, based on the total volume of the substrate.
 18. The selectivecatalytic reduction article of claim 13, wherein the first catalyticcoating and the second catalytic coating are in a layered or zonedconfiguration.
 19. The selective catalytic reduction article of claim 1,wherein the substrate is a porous wall-flow filter or a flow-throughmonolith.
 20. An exhaust gas treatment system comprising: a selectivecatalytic reduction article according to claim 1; and a reductantinjector in fluid communication with and upstream of the selectivecatalytic reduction article.
 21. The exhaust gas treatment system ofclaim 20, further comprising one or more of a diesel oxidation catalyst,a soot filter, a lean NOx trap (LNT), and an ammonia oxidation catalyst.22. A method for treating an exhaust stream containing NOx, comprisingpassing the exhaust stream through a selective catalytic reductionarticle or an exhaust gas treatment system of claim
 1. 23. A method foridentifying a catalytic material that is stable toward aging, the methodcomprising: providing a plurality of samples that each compriseparticles of a copper-containing molecular sieve containingion-exchanged copper as Cu⁺² cations and as Cu(OH)⁺¹ cations; subjectingthe particles of the copper-containing molecular sieve to DiffuseReflectance Infrared Fourier Transform (DRIFT) spectroscopy so as toevaluate perturbed T-O-T asymmetric stretching vibrational peakscorresponding to the Cu⁺² cations in the copper-containing molecularsieve and perturbed T-O-T asymmetric stretching vibrational peakscorresponding to the Cu(OH)⁺¹ cations in the copper-containing molecularsieve; and selecting one or more of the samples wherein thecopper-containing molecular sieve exhibits a ratio for an integratedpeak area of the perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu⁺² cations to an integrated peak area of theperturbed T-O-T asymmetric stretching vibrational peak corresponding tothe Cu(OH)⁺¹ cations that is ≥1.
 24. The method of claim 23, wherein apercentage of the total integrated peak area that is attributable to theperturbed T-O-T asymmetric stretching vibrational peak corresponding tothe Cu⁺² cations is calculated by dividing the integrated peak area forthe perturbed T-O-T asymmetric stretching vibrational peak correspondingto the Cu⁺² cations by a peak integration area for the perturbed T-O-Tasymmetric stretching vibrational peak corresponding to the Cu⁺² cationsand the perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu(OH)⁺¹ cations combined, and wherein the methodcomprises selecting one or more samples wherein the percentage of thetotal peak integration area that is attributable to the perturbed T-O-Tasymmetric stretching vibrational peak for Cu⁺² cations is ≥50%.
 25. Themethod of claim 24, wherein the plurality of samples is subjected to theDRIFT spectroscopy in a fresh state, and wherein the method furthercomprises: aging the plurality of samples at a temperature of about 800°C. for a time of about 16 hours in the presence of air with an H₂Ocontent of about 10 mol % to form aged samples; subjecting the agedsamples to the DRIFT spectroscopy; and selecting one or more of thesamples wherein the contribution to the total integrated peak area bythe perturbed T-O-T asymmetric stretching vibrational peak correspondingto the Cu⁺² cations for the one or more samples in an aged state isincreased by ≤20% relative to the contribution to the total integratedpeak area by the perturbed T-O-T asymmetric stretching vibrational peakcorresponding to the Cu⁺² cations for the one or more samples in thefresh state.
 26. A method of manufacturing a catalytic article, themethod comprising developing a process for preparing a first compositioncomprising copper-containing molecular sieves; analyzing at least asample of the first composition using DRIFT spectroscopy to determinethe relative amount of Cu⁺² and Cu(OH)⁺¹ in the first composition basedon a comparison of intensities of perturbed T-O-T asymmetric stretchingpeaks corresponding to the Cu⁺² and Cu(OH)⁺¹ selecting the process forcommercial manufacturing of the first composition if the contribution bythe perturbed T-O-T asymmetric stretching peak corresponding to Cu⁺² tothe total integrated peak areas of the perturbed T-O-T asymmetricstretching peaks is ≥50%; applying the commercially manufactured firstcomposition made by the process to a substrate to produce the catalyticarticle.